1. Field of the Invention
The present invention relates to a radio communication system, a radio communication apparatus and a computer program. More particularly, the present invention relates to a radio communication system for making a PCA (Prioritized Channel Access) in a band reserved in advance, a radio communication apparatus employed in the system and a computer program implementing functions of the apparatus.
2. Description of the Related Art
In recent years, as a method of constructing a small-scale network for carrying out radio communications, there is generally adopted a method of using a radio communication system conforming to methods according to IEEE802.11 as a radio LAN (Local Area Network). In addition, attention is recently being focused on a radio communication method using a UWB (Ultra Wide Band) communication system. As a radio communication method using the UWB communication system, there was considered a method of carrying out high-speed radio communications by using a PAN (Personal Area Network), which is a network having a range narrower than that of a radio LAN.
As one of access control methods of the PAN (Personal Area Network) in the UWB communication system, there was considered a method of defining a distributed MAC (Media Access Control). In the distributed MAC, there was defined a method for carrying out a communication in a stable manner by using a DRP (Distributed Reservation Protocol). This defined method is a method for providing a time slot known as a MAS (Media Access Slot) in a predetermined super frame period, reserving the MAS and setting utilization of the MAS.
In addition, in accordance with the DRP (Distributed Reservation Protocol), a communication apparatus for carrying out a communication is capable of utilizing media by exclusively occupying the media. Thus, the method can be defined as a method capable of carrying out a communication in a stable manner.
In the distributed MAC (Media. Access Control), on the other hand, there has also been prescribed a communication method based on the PCA (Prioritized Channel Access) technique as a method for carrying out a communication without making a reservation by using the DRP (Distributed Reservation Protocol). With the communication method, a communication can be carried out with ease by using a period, for which reservation using the DRP is not set.
In addition, Japanese Patent Laid-open No. 2004-153558 (Patent Document 1) discloses a method of setting CP_Min_Duration so as to assure a possible minimum communication in a CP (Contention Period) for any communication such as inspection of a web besides reserved communications such as transmissions of images.